Preparation of aromatic dinitriles



Patented Mar. 7, 1939 I UNITED STATES PATENT OFFICE 2.14am PREPARATION OF DINITRILES Arden Gan-ell Decm, Wilmington, and Wilbur Arthur Luier, Elsmere, DeL, assignora to E. I. du Pont de Nemours & Company, Wilmingto Del., a corporation of Delaware No Drawing. Application May 29, 1937, Serial No. 145,508

8 Claims. (Cl. 280-485) I Lowe, issued September 15, 1036, there is disclosed a catalytic process for the manufacture of aryl dinitriles which comprises passing a gaseous mixture of ammonia and an orthoor peri-aromatic dicarboxylic acid, anhydride, amide or imide over a suitable dehydrating catalyst at elevated temperature's. As dehydrating catalysts are mentioned silica, alumina and thoria. In a con- 20 tinuing application Serial No. 94,284, flied Ausult 4, 1938, the same inventors further disclosed that by adhering to certain specific operating conditions of temperature, time of contact, and amm'onia-concentration, the reaction may be, con- 5 trolled to give the main product in high yields and essentially free from by-products. On the other hand, it has been established that under certain conditions the above process yields substantial amounts of aromatic mononitriles in 30 addition to aromatic dinitrlles (cf. copending application of Howk and Wortz, Serial No. 95,035, filed August 8, 1936). The present invention. is ln-the nature of an improvement upon said prior processes, and has 35 as its object to -provide a catalyst which is particularly eiilcient, economic and durable under the conditions of operation.

We have found that if phthalic acid, anhydride,

above cited priorart. In the first place, we have found that when a catalyst comprising basic aluminum phosphate is employed the reaction is readily controllable to produce high yields of dinitrile in ahigh state of purity. Secondly, we 5 have found that basic aluminum phosphate, basic aluminum sulfate, and mixtures of the two are particularly sturdy, and give consistently high yields under continuous use, whereas with other dehydrating catalysts the yield tends to drop oil after prolonged use. Furthermore, while some of the other dehydrating catalysts decompose or lose their activity upon regeneration, the preferred catalysts of our invention may be repeatedlyregenerated with substantially no loss in catalytic activity. This is a very important property of aluminum phosphate catalysts from a practical point of view since it reduces catalyst costs. Altogether then, our invention renders the entire process particularly economical when practiced on a commercial scale.

Basicaluminum phosphate as employed in this application refers to the hydrate of aluminum phosphate obtainable by precipitating an sulfate. For want of a standard term, we shall refer generically to all such compositions, whether consisting of pure aluminum phosphatehydrateor admixed with sulfates of aluminum,

as "phosphated-alumina hydrate". A typical commercial product of this series possesses the as following compositionz' Percent A120: 38 to SO: 10 toli P205 15 to 1'7 40 N520 0.1 to 0.2 Fe

Without limiting our invention to any particular procedure, the following examples are otherwise stated.

Example 1 A vigorous stream of ammonia is passed at the rate of 255 liters per hour through a tube containing 500 cc. of a basic aluminum phosphate catalyst, which is in the form of small pellets.

The catalyst is maintained at'a temperature of vaporized, and introduced into the ammonia stream at the'rate of 99 grams per hour. The

vapor stream issuing from the tube is passed into a cooled receiver where the product separates as a finely divided powder. Water vapor isvented to a separate trap. This powder is stirred with approximately 5 times its weight of warm benzene until no more of the solid dissolves. Filtration removes 42 grams of unchanged o-phthalimide corresponding to 2.7% of the amount charged. The filtrate is cooled and o-phthalonitrlle separates in white needles, M. P. 140-141 C. The benzene solution is steam distilled to yield, in addition to solvent, 0.9% of benzonitrlle. The solid residue is recrystallized from hot water to recover the remainder of the o-phthalonitrlle. This in combination with that which crystallized from benzene amounts to 951 grams, which represents a molecular yield of 91.8%. An alternative method of refining, which yields o-phthalonitrile of reasonably good quality, comprises extracting the crude powder with cold 5% caustic soda solution to dissolve phthalimide and other alkali soluble by-products. The mixture is filtered, the filter cake washed thoroughly with cold water, and dried. If so desired, this product is further refined by distillation or sublimation.

A basic aluminum sulfate catalyst when employed under the above conditions, gives equally good results, either aloneor when admixed with basic aluminum phosphate.

Example 2 A stream of-ammonia is passed at the rate of 4.25 liters. per minute through a tube containing 500 cc. of a basic aluminum phosphate catalyst maintained at 450 C. 1212 grams of o-phthalic anhydride are vaporized, and introduced into the ammonia stream at the rate of about 100 grams per hour. In traversing the catalyst bed, the 'o-phthalic anhydride-ammonia mixture is converted mainly to o-phthalonitrilef 18.8 and the contact time 2.52 seconds.

l'mplc 3' v I A vapor mixture of o-phthdlimlde and ammnnia containing 6.9 mols of ammonia per mol of o-phthallmide is passed over 500 cc. of a phosphated-alumina-hydrate catalyst (for. instance,

Parts mentioned are "by weight, unless 1187 grams of o-phthalimide are =o-phthalimide, and benzonitrile.

the commercial catalyst having the composition hereinabove tabulated) heated to 475 C. During a period of 12 hours, 1383 grams of o-phthallrnide are treated in this manner. The products are condensed and worked up according to the procedure described in Example 2, above. There is obtained 29.5 grams of unchanged o-phthalimide, 1165 grams of o-phthalonitrile, and 1.1 grams of benzonitrile. The conversion to ophthalonitrile is 88.3% of theory. The contact time is 4.70 seconds.

Example 4 654 grams of o-phthalimide are processed according to the above procedure under the following conditions:

Ratio of ammonia to o-phthalimide Duration of run "hours" 6 Catalyst volume cc 500 Catalyst Phosphated-alumina-hydrate Temperature 475C. Contact time seconds 2.61

The products obtained consisted of 14.6 grams of unchanged o-phthalimide, 531 of o-phthalonitrile, and less than 1 gram. of benzonitrile.

The conversion to o-phthalonitr-ile is 91.9% oftheory. 1

. Example 5 25,020 grams of o-phthalh'nide are processed according to the procedure described under Example 4, above, under the following conditions:

The average conversion to o-phthalonitrile in the above experiment was 87.4% of theory.

Example 6 I 500 cc. of hydrated aluminum sulfate catalyst in the form of pellets is charged into a vertically mounted catalyst tube and heated to a temperature of 425 C. Ammonia is passed through the catalyst bed at the rate of 0.15 cu. ft. per minute (Standard temperature and pressure). o-Phthalimide is vaporized and passed in with the ammonia at the rate of 1.83 grams per minuteduring a period of 12 hours. Under/these conditions the ammonia-phthalimide ratio is 14:1 and the contact time 2.8 seconds. The gaseous products issuing from the catalyst tube are condensed to form a faintly yellow powder which is treated according to the procedure of Example 1 to remove o-phthalonitrile, unchanged Hem 1315 grams of o-phthalimide processed, there is obtained 1048 grams of o-phthalonltrile, 49.9 grams of phthalimide, and 8.3 grams of benzonitrile.

These amounts correspond to molecular yields of 91.5%, 3.8%, and 0.9% respectively. Similar resuits are obtained in retestlng the catalyst after regenerating by treating with air at elevated temperatures.

For the sake of comparison, 'we are tabulatins below a number of miscellaneous dehydrating catalysts tested by us under various conditions. and the yields thus obtained. It will be noted lyst tempera- 2,149,280 superior may be carried out at elevated cata tures ranging from about 300 C. to about 550 C.

In the foregoing examples we have mentioned 30 three other important variables: space velocit time oi contact, and ammonia ratio.

' The space velocity and time 01. contact are interdependent variables and serve as a measure of the rate at which the gaseous reactants pass 35 through the catalyst. "Space velocity is defined as the number of volumes oi gas, calculated as at I standard conditions, that pass through a unit volume of catalyst in 1 hour. Time of contact is defined as the time in seconds that is required 40 by the gaseous reactants to traverse the g capable y appreciable loss in ysts employed in perature that basic aluminum phosphate gives yields to each and every one of them.

5 w n m oza ccnnom 0 3 mm... w m 7 0 60 w o fiusun m n m. My mm 7 7 19 m $5.355 on 5 33 3383 QB; M 2 Z 5 2 2 7 7 5 2? 32.6 5 5 M m 0 31 2552 m m no 7 48 .53 r 8a @085 in gen. m mm 86 6 70 2 u... on wooden =o E m m m .50: on @893 m M M W m 1 8 5 5 5 25: M 0 00 L t a n n u n m m n m nnmmamnmm was 1 a s i 0 dum nun u mm w a M m mnw m u w nmn w .H" 0 m a n m .md mmmm .ml w mi.mua .b sm nm m r h mwm m m mnflu nm m ummmmmmm mmm mmmmm A TTACVJTmM m APn restate am mmmmw m mum mm no. o E. W n nun um H m m m m N I r ll n "i m w M m m m .n n u n m m m I a 0 0 m m n pp 8 m P 5 superior yields, phos- -alumina-hydrate catalysts have the advantage, already noted above, of standing up The regeneration of the cats] this invention is effected by burning ofi the carbonaceous deposits at an elevated tem in a stream of an oxygen-containing gas. This In addition to giving phated well under continued use, and of bein of regeneration without an catalytic activity.

process may be carried out either in situ or b removing the spent catal fie y yst to a-separate mufentire fle furnace. Phosphated-alumina-hydrate cataspace occupied by. the catalyst at the temperature lysts revivi d in this manner are essentially and pressure of the reaction, assuming no change equivalent to fresh, unused catalysts as is shown in volume. The time of contact. and space by the following example: velocity may be calculated from each other by es the following expression:

. 273X60X60 (273+Temp. in C.) space velocity In the practice of this invention it is most advantageous to operate with contact times ranging from about 2 seconds to about 12 seconds.

ratio"'is an expression of the phthalic 65 amide, imide, etc., that are mainpassed per unit In practice, we prefer to use a molal excess of ammonia ranging from about 6 to about 20 times that theoretically required.

3 au- 65 pounds that are capable of reacting with ammonia to produce diamides or imides. In addition, to phthalic acid maS be applied dicarboxylic com- '70 1,8-naphthalic chlorophthalic anhydride, etc., producing the respective dinitriles.

Time of contact The ammonia relative concentrations 0! ammonia and anhydride, acid tained in the reaction chamber during the reaction. A numerical value for ammonia ratio is obtained by dividing the number 0! mols of ammonia passed per unit of time by "the number of $0 mols of phthalic anhydride, etc of time.

The process of this invention is broadl plicable to aromatic dicarboxylic com and its derivatives the process successfully to other aromatic pounds such as terephthalic acid anhydride,

- Other variations and modifications will be readily apparent to those skilled in the art ortho-phthalp ss n ters per minute.

is passed in with f 115.5 grams per g to the prothere is obtained o-phthaliznide and respectively; showing that the phosprolonged use.

that theabove examples e purpose of illustration,

and that this invention is capable of wide variation and modification without departing from the spirit thereof.

Example 7 A 500 cc. sample of phosphated-alumina-hydrate catalyst is revivified after 230 hours of continuous use in the preparation of onitrile from ortho-phthalimide, by combustion of the carbonaceous deposits in a stream of air at 450 to 500 C. This catalyst is then again used'in the conversion of ortho-phthalimide to o'rtho-phthalonitrile, for instance, as follows:

The converter tube and catalyst are maintained at a temperature of 475 C. while ammonia at the rate of 3.9 11 vaporized ortho-phthalimide co the ammonia at the rate 0 hour. Upon working up the product from 1385 grams of ortho-phthalimide accordin cedure'described in Example 1 83.5 grams of unchanged orth 1063 grams of 'ortho-phthalonitrile. These val- -ues correspond to molecular conversion of 6.1

and 88.2%, phated-alumina hydrate catalyst has sufiered little or no deterioration through It will be understood are given merely for th Broadly speaking, the process of this invention We claim:

1. A process for the manufacture of aryl dinitriles which comprises heating a gaseous mixture comprising a molecular excess of ammonia and a member of the group consisting of orthophthalic acid, ortho-phthalic anhydride, phthalamic acid, phthalimide, and phthalamide at a temperature between 300 and 550 C. for a period of time between about 2 seconds and about 12 seconds in the presence of a catalyst'selected from the group consisting of basic. aluminum phosphate, basic aluminum sulfate, and mixtures of the two. i

2. A process as in claim 1, in which the quantity of ammonia is at least 6 times the amount theoretically required to react with the organic compound undergoing conversion to phthalonitrile.

g 3. The process of producing an aromatic orthodinitrile' of the benzene series which comprises passing a gaseous mixture of an ortho-dicarboxylic acid imide oi the benzene series and an excess of ammonlain contact with a catalyst comprising essentially hydrated aluminum phosphate at a temperature between about 4400 and 500 C. and at a time of contact between about 2 and 12 seconds.

4. The process of claim 3 in which the moiecular ratio of ammonia to the aromatic dicarboxylic imide is between 6 and 20.

5. The process which comprises passing a mixture of phthalimide vapor and excess ammonia over a'hydrated aluminum phosphate-aluminum sulfate catalyst, heated at a temperature between 400 and 500 C., at such a rate that a contact time between 2 and 12 seconds is maintained, and thereafter separating water and unreacted ammonia from the recovered phthalonitrile.

6. The process of producing phthalonitrile, which comprises passing a mixture of ammonia. and phthalimide in a molal ratio of between 6 and 20, at a temperature between 400 and 500 C.

phosphate, the rate of flow of gases being con;

trolled so that the resulting contact time is between 2 and 12 seconds.

8. The process of producing phthalonitrile, which comprises passing a mixture of ammonia and phthalimide in a molal ratio of between 6 and 20, at a temperature between 400'and 500 C.

over heated hydrated aluminum sulfate, the rate of flow of gases being controlled so that the resulting contact time is between 2 and 12 secondsr ARDEN GARRELL DEEM. WILBUR AR LAZIER. 

